Silica films obtained by a sol-gel reaction have been widely known as a film having a high degree of hardness. However, when a film is obtained by using only silica, cracks are generated in the film. Therefore, anti-cracking properties of the silica film are improved by using an organic polymer having film forming properties and toughness together with silica.
As a composition which provides a silica film containing an organic polymer, a uniform solution in which an amide group containing non-reactive polymer and hydrolysable metal oxide such as a specific silane are dissolved uniformly in an alcohol solvent has been suggested (For example, Patent Document 1). When the uniform solution is used and the hydrolysable metal oxide is subjected to a hydrolysis polycondensation reaction to make it a gel, an organic•inorganic complex transparent homogeneous substance in a film state can be obtained by keeping it in a film shape until the gelatinization of the uniform solution and removing the solvent. However, the uniform solution contains an alcohol solvent; therefore, it has been desired to change the alcohol solvent to an aqueous solvent in order to decrease environmental load.
In addition, as a silica film forming solution containing an aqueous solvent, a coating solution which comprises a silane compound, organic strong base, and a polar group containing polymer, and in which the silane compound is dissolved in the presence of the organic strong base, has been suggested (for example, in Patent Document 2). However, the coating film obtained by the coated solution has an insufficient degree of hardness and insufficient abrasion resistance in the filed of an inorganic coating film including a coating material. Therefore, it has been desired to improve these properties.
Patent Document 1: Japanese Unexamined Patent Application, First Publication No. H3-212451
Patent Document 2: Japanese Unexamined Patent Application, First Publication No. H11-271521